1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Finding intervals of increasing, decreasing, concavity and inflection points

  1. Nov 23, 2008 #1
    1. The problem statement, all variables and given/known data

    let g(x)=2x^5-10x^3=15x-3. find the intervals on which G is increasing and decreasing. and find the intervals of concavity and the inflection points

    2. Relevant equations



    3. The attempt at a solution
    i know how to find the increasing and decreasing intervals. i just cant figure out where the graphs cross the x axis. and the concavity intervals i cant figure out
     
  2. jcsd
  3. Nov 23, 2008 #2

    Mark44

    Staff: Mentor

    Show us what you've done...
     
  4. Nov 23, 2008 #3
    well i found the derivative to be 10x^4 +30x^2+15 but when i graphed it i couldt figure out where it crossed the x axis
     
  5. Nov 23, 2008 #4

    Mark44

    Staff: Mentor

    Here's what you showed in your first post:
    What's with that '=' right after the x^3 term? Did you mean that to be a '+'?

    Assuming that's the case, g(x) = 2x^5 - 10x^3 + 15x -3
    Your calculation for the derivative -- g'(x) is its name -- is incorrect.
     
  6. Nov 24, 2008 #5
    I think from equating first derivative to zero u can easily find the point where no change occurs and beyond that it go on changing. and from 2nd derivative u can find the inflection points. Am I correct????
     
  7. Nov 24, 2008 #6

    Mark44

    Staff: Mentor

    Equating the derivative to zero gives you the values where the tangent lines are horizontal, which can help you find local maxima and minima.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?